As an example of a portable working machine having a structure obtained by joining a handle with a main body casing with a vibration-proofing mechanism interposed therebetween, there is an engine chain saw. The engine chain saw uses an engine (an internal-combustion engine) as a driving source, and a front handle and a rear handle are joined with a main body casing (an engine casing) storing the engine. A user performs tree sawing work while applying a load to the rear handle. Also, in a case where a guide bar for guiding a saw chain is caught in a tree during sawing, it is required to push or pull the rear handle. For this reason, a vibration-proofing mechanism provided between the rear handle and the main body casing having the guide bar fixed thereto needs a structure for regulating a movement amount of the rear handle. Therefore, in a case of installing a spring type vibration-proofing mechanism at the front end portion of the rear handle, in order to regulate the movement amount, a stopper is provided in a spring. However, even if the stopper is provided in the spring, if a large load is applied, the movement amount and inclination of the rear handle may not be appropriately regulated. For this reason, there has been suggested a vibration-proofing device having a separate vibration-proofing mechanism at a position at an opposite side of a fixing portion of the spring (see JP-A-2002-178223, for instance).